HTMLArea swap elements
HTMLArea swap elements

Added a generic method to swap two TextElements within one HTMLArea. The
methods .swapDown() and .swapUp() now use this method to perform their
swap action.

The TextElement method .focus() now also sets the $current of its
HTMLArea.

Also fixed a spelling error 'isFocused', which should have been
'isFocussed'.

ericcornelissen/html-area,ericcornelissen/htmlarea,ericcornelissen/htmlarea